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Phenylketonuria (PKU) is a rare metabolic disorder which, when left untreated, can lead to profound and irreversible mental disability. Dietary treatment prevents most of the neuropsychological complications. However, the diet is difficult to maintain, adherence to it is often poor and deficits in cognitive (brain) functions (e.g. memory, attention) are still observed in patients.

We are currently looking for healthy controls (18+ years of age) to participate in a short (2 sessions of ±15 minutes each) online study looking at cognitive functioning in adult PKU patients who differ in their level of adherence to diet. The study consists two test sessions using a few online (cognitive) tasks (±15 minutes).

The cognitive tests are a series of computerized tests of mental performance. The tests will assess brain functions such as memory, reaction time, attention and problem solving skills. The tests are not designed to trick you. You just have to complete the tests to the best of your ability. You will have the opportunity to practice the tests and familiarize yourself with the procedures during the first online test session.

By participating in this research and completing both test sessions you have a chance to win one of 50 Amazon vouchers worth £10 ($12.50) each!

To check your eligibility for participating in our research (e.g. to assess whether you match all criteria (age, gender, occupational status/educational level) to act as a healthy control to one of the PKU patients included in our research), we would like you to answer a short screening questionnaire (±5 minutes).

Furthermore, you will need to create a unique participant ID. This participant ID is used so your answers will remain anonymized, but the researchers will be able to identify your data if you wish to withdraw. All data collected in this study will be confidential and stored separately from any identifying information you choose to provide. Only the researchers mentioned below will have access to your data but they will not be able to identify you.

You may withdraw from the experiment at any point, without reason or consequence, by simply closing your browser. If you wish to withdraw your data once it has been submitted, you can do so by e-mailing the research team and stating your unique participant ID.

This research has been granted ethical approval by the School of Psychology Ethical Review Committee, University of Leeds, United Kingdom, reference number 17-0064 (08/02/2017).

Thank you in advance for your time, your responses are highly appreciated.